It sounds like a simple request in a city known for steamy nightclubs, Bacchanalian beach parties and Carnival parades featuring nude starlets donning only a "tapa-sexo," a leaf-sized patch of fabric that serves, literally, as a sex covering.

But there was a hitch in the recent casting call. The women wanted by Mocidade Independente Padre Miguel, one of Rio de Janeiro's best known Carnival troupes, had to be silicone-free.

In salute to a bygone era, Mocidade wanted Carnival dancers without the globular breasts and "bumbum," or buttocks, that now dominate the annual spectacle, a week-long party meant to purge sin before the Catholic season of Lent.

"It wasn't easy," says Paulo Menezes, the artistic director for the group, one of the 12 top-tier troupes that will march in Rio's Carnival starting on March 2. "Most of the women who want to take part in something like this have all had some surgery."

Beauty-obsessed Brazil boasts one of the world's highest rates of cosmetic surgery. With two-thirds the population, it runs a close second to the United States in its number of plastic surgeons and the number of surgeries performed, according to the International Society of Aesthetic Plastic Surgeons.

Carnival itself is also about artifice.

The show at Rio's Sambadrome, the floodlit concrete parade ground, is a multimillion-dollar extravaganza of costumes, music and theater. Each samba school, as the troupes are known, is a regiment of dancers, drummers and divas. Mocidade alone will march 4,000 people.

The natural bodies at Mocidade are seen as a small nod to a trend that has pushed Carnival at least a little bit back toward its roots. Though still dominated by the big parades, broadcast nationwide each night, Carnival in recent years has enjoyed a rebirth of the block parties and neighborhood revelry from which the big event sprang.

"There is more variety than before and a desire for things to be a little less produced," says Haroldo Costa, a Carnival veteran and author of a history of the festival. "It is making things more authentic and more popular."

In Rio, home to Brazil's best-known Carnival celebration, 5 million people are projected to join the party this year, a fifth of them tourists. The event will pad the local economy by more than $700 million, according to city figures.

THE SEARCH

To find its 22 implant-free participants, who will preside over the first of the school's nine parade floats, Mocidade last October put the word out via social media. Applicants were asked to submit a photo, basic personal details and their body measurements, necessary for tailoring the skimpy, but costly hose, harness, boots and headdress that those chosen will wear.

Each costume, at a cost of about $1,200, is bedecked with rhinestones and studs and further adorned with pheasant and rooster feathers. The cost, along with that of the floats and other expenses, add up to a $2.5 million budget at Mocidade, which is financed by television revenue, government cultural subsidies and the backing of school supporters.

At first, the response was slow. Many applicants did not quite understand the requirements.

A few submitted photos that left no doubt of surgical intervention. Some applicants only sent photos of their breasts - not enough for the school to make an informed decision. Other applicants, including a 60-year-old, did not quite fit the profile.

"She wasn't exactly what we were looking for," said Menezes, in his office above a cavernous warehouse where the school is making final parade preparations. Dozens of workmen below are still welding and painting floats and giant sculptures of oxen, farmhands and other rural caricatures that will adorn them.

What Menezes did want among the applicants was variety. It took several months, but he got it.

Those chosen range in age from 18 to 46. Some are tall, some are short. None have the Photoshop features that leap from magazine covers.

"I never thought I would be able to take part in something like this," says Duza Alves Barbosa, the eldest of the women, who works as a vendor at a jewelry store. "I run, I take care of myself, but I don't have one of those bodies you see on TV."

On Monday night, a group of the women met at a square next to a train station in the gritty Rio suburb of Bangu. Thousands of Mocidade members, most dressed in its trademark green and white, converged on the square for one of their last rehearsals.

Shortly before midnight, the procession began, propelled by the school's legendary percussionists, a battery of 280 drummers known as "Não Existe Mais Quente," or There is None Hotter. Glauce Costa, a 32-year-old secretary and mother of one, stomped and shook, the tassels of her white dress gyrating.

She will be more constrained atop the small plinth each woman will stand upon while the float is under way.

"There I'll just smile and wave," she said. "It's a shame we can't dance. As long as we're topless, we may as well have some bounce."

There will be plenty of motion elsewhere, though.

The women, after all, are just the tip of a long and diverse procession. And Mocidade officials insist they are not trying to make any sort of statement against cosmetic surgery.

In fact, Menezes said the woman who will carry the Mocidade flag, a key figure in any Carnival procession, has implants.

Jessica Gomes dos Santos, the youngest of the unaltered, says she might even join the augmented once she finishes psychology studies in college. "I could use a bigger bumbum," she says, tapping her trim hips.